1. Field of the Invention
This invention relates to a rod seal device for the Stirling engines and more particularly to a rod seal device for the Stirling engine which utilizes a guide piston at the power take-off structure as a part of the compressor for an air-conditioner using Freon gas as the working fluid.
2. Description of the Prior Art
In a prior art seal device for the Stirling engine shown in FIG. 1, Stirling engine generally indicated as numeral 1 includes operating piston 2 in the cylinder and a compression chamber 6 defined by the piston 2 and the cylinder. This compression chamber for an operating space is connected to anexpansion chamber (not shown) through cooler, heat exchanger and heater (all not shown). The operating piston 2 is connected to the guide piston 4 through a rod 5 which extends from the crank case 3 into the cylinder of the Stirling engine 1. The crank case 3 and the guide piston 4 will be served as the power take-off of the engine 1. The operating piston 2 reciprocates by the operating fluid such as for example Helium gas or Hydrogen gas in the compression chamber 6. Suchreciprocable movement of the piston 2 will reciprocate the guide piston 4 to compress a working fluid in the chamber 14 for operating the air-conditioner. Freon gas is usually used in the fluid chamber 14 for operating an air-conditioner. The seal device between the two pistons 2 and 4 includes from left to right in FIG. 1 gas seal 7, intermediate gas chamber 8, scraper seal 9, high-pressure oil chamber 10, oil seal 11, low-pressure oil chamber 12, and oil seal 13. In this conventional device, the high pressure oil chamber 10 is connected to the compression chamber 6 through high pressure oil reservoir 15, oil filter 16 and check valve 17. Further, the high pressure oil reservoir 15 is connected to the intermediate gas chamber 8 to keep the pressure in both chamber 8 and the reservoir 15 to the minimum pressure level of the operating gas pressure in the chamber 6. In other words, the pressure in the high pressure oil chamber 10 is kept to maintain the minimum operating gas pressure and the leakage of operating gas into the chamber 10 can be recovered by returning to the compression chamber 6 via check valve 17. The low pressure oil chamber 12 is connected to low pressure oil reservoir 16 which is open to the atmospheric pressure and the leakage of operating gas or the operating gas for the air-conditioner into the chamber 12 can be discharged to the atmosphere from the low pressure oil reservoir 16. This device, however, has a drawback that the two operating gases Helium and Freon may be mixed at the high pressure oil chamber 10 one from the chamber 6 and the other from the chamber 14 through the peripheral surface of the rod 5. The Freon gas may cause chemical reaction under the high ambient temperature thereby to produce an undesirable acid which causes corrosion of the various components of the assembly.